Tuning indicator tube



June 28, 1938.

H. M. W AGN ER TUNING INDICATOR TUBE Filed Sept. 29, 1937 R m m m gf/afikm. WAGNER ATTORNEY.

Patented June 28, 193

amazes G IUATGR ll Herbert M. Wagner, Newark, N. it, smaller, by

mesne 88S i to to litadio Corporation at -America, New York, N. Y a coration or Delaware Application September 29, 193?, Serial No. 166,251

m vention is an improvement over a device of the general character described and claimed in my Patent No. 2,051,189, issued August 18, 1936.

The tuning indicator described in the patent referred to above comprises an envelope having within it a straight thermionic equipotential cathode provided with two separate emitting sections, one of which is' surrounded by amplifier elements which may comprise a control grid and anode, and the other of which is surrounded by 20 the tuning indicator elements of the tube consisting of a straight control electrode parallel to the cathode and a dish-shaped anode coated on its inside surface with fluorescent material, the anode being concentric with and surrounding the cathode and the control electrode. In operation electrons flow from the cathode to the fluorescent anode or target with suflicient velocity to bombard the fluorescent anode and render it luminous. The control electrode is connected to 30 the amplifier anode and the tube so connected into a receiving circuit that when the circuit is tuned to resonance with an incoming signal the luminous portion of the plate is of a predet'ermined width, preferably the device is so connected that the luminous portion of the anode of the tuning indicator section of the tube is of maximum width, the dark portion of minimum width, when the circuit is tuned to resonance, and preferably the entire anode is made fluorescent and the dark portion disappears.

In some cases with the'usual voltages applied to the anode and with space charge limitation of the current between cathode and anode, the life of the fluorescent coating is made comparatively short because of the large current the fluorescent anode receives. In addition the increased current to the fluorescent anode causes undue heating and undesirable results. 7 Because of these factors the voltages which can be applied 50 to the fluorescent anode are limited.

It is the principal object of my invention to provide an electron discharge device of the type described, particularly suitable for use as a tuning indicator, in which the life of the fluorescent coating is increased and in which the heating ef- (Q'Jl. 250-275) fects caused by the fluorescent anode current. are, minimized, and in which the range of voltages which can be applied to the fluorescent anode is I extended.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 shows an electron discharge device embodying my invention with parts broken away'to show details of construction; Figures 2 and 3 are top views with parts removed to show the tuning indicator portion of the tube and the pattern of it light under difierent voltage conditions; Figure 4 is an enlarged perspective view of the electrode construction of the tuning indicator section of a tube shown in Figure 1; Figure 5 is a perspective with parts broken away of a modification of the electrode construction of ,the tuning indicator section oithe tube, and Figure 6 is a partial transverse section taken along the line 6-6 of Figure 5; and Figure 7 is a circuit diagram embodying a tuning indicator tube made in accordance with my invention.

The electron discharge device or tuning indicator tube shown in Figure 1; comprises an evacuated envelope it provided with the usual stemand press ii and base it. Supported from the press are a cathode it, preferably the conventional indirectly heated equipotential type, and a grid it concentric and preferably coextensive with and surrounding the cathode, and an anode i5 surrounding the grid. While shown as a 36 triode this section of the tuning indicator tube could be of any other multi-element type.

The tuning indicator elementsof the tube are placed at the upper end of the mount. The

cathode it is extended upwardly and provided 40 with a second emitting section is adjacent which is placed the control electrode H which may be a rod or a vane shaped from sheet material and placed edgewise to the cathode. This control electrode it is supported from and connected at it to one of the side rods of the anode i5. Surrounding and concentric with the emitting portion it of the cathode is an anode i9 shaped like a dishpan having a collar 2t and a coating 2i fluorescent under electron bombardment. The

electrons emitted from the cathode and striking the anode with sufiicient velocity, cause it to fluoresce. A cap 22 is positioned over the top end of the cathode it to confine the electrons to the emitting portion, the collar 20 preventing electrons from reaching the glass walls of the envelope over the top of the anode. The cap 22 is supported from the dishpan-shaped anode and preferable electrically connected thereto by means of side rods 23 positioned 90 from the control electrode as best shown in Figure 4. The cap 22 also serves as an electrostatic shield to prevent any straycharges that might develop on the glass envelope from affecting the'electron stream from the cathode to the fluorescent anode.

In this type of tuning indicator the electrons travel radially outward from the cathode to the fluorescent coating on the anode in a wide beam. The extent of the surface of the anodereached by the electron beam is determined by the voltage on the control electrode H. The less negative this electrode is with respect to the anode 20, that is the more positive with respect to the oathode IB, the greater the area of the anode covered by the beam and the greater .the area of the fluorescent portion of the anode. The control and well defined, there can be a high concentration of electrons at theedges of the luminous areas of the anode so that the edges are brighter and stand out more prominently, a high current to the luminescent anode and hence high luminosity is obtained with low anode voltages, and the control electrode can be coupled directly to an amplifier. The tube is not critical to variations in cathode temperature, and it can also be used with either alternating or direct voltages and currents.

The tube is viewed from the end so that the pattern of light is viewed as shown in Figures 2 and 3. As shown in Figure 2 when the control electrode is at a potential near that of the cathode the anode fiuoresces only over the area indicated by the shaded lines. comes more positive more of the surface of the anode fluoresces until at a predetermined voltage the entire surface of the anode 20 fiuoresces. This is the pattern which is shown in Figure 3 and which is obtained when the circuit in which the tube is used is tuned to resonance. Under these conditions the edges of the luminescent portion of the fluorescent anode Just touch so that the dark space is at its minimum or just disappears.

In accordance with my invention I position around the cathode IS a helically wound grid I611, which is close to and connected at its ends to the cathode sleeve. In a tube made in accordance with my-invention I used for this purand. distinct.

pose a wire having a diameter of 0.010 inch wound fifty turns to the inch. The helix diameter is only a'few thousandths of an inch larger than that of the coated cathode. I found that in a tube made in accordance with my invention the moving fluorescent edges of the beam were sharp I Using a grid in the manner described will decrease the fluorescent anode current so that both the life of the coating and the heating effects described above are substantially eliminated, and will permit the extension of the anode voltages whichcan be applied to the fluorescent anode.

In a modification of my invention shown in Figures 5 and 6 I provide the grid I641 with a pair of side rods Nib upon' which the grid is wound.

The grid is secured to thecathode by having opposite ends of the two side rods welded to the cathode. In order to compensate for the elecsource of voltage supply 26.

As the electrode be-- tron shadow which these side rods would cast on the fluorescent coating I provide the top cap 22 with the wide ribbon support members 23a positioned opposite and close to the grid side rods. These support members being at a positive potential with respect to the side rods counteract the influence of the negative potential of these side rods so that the shadow which would normally be caused by these side rods is practically eliminated on the target or fluorescent anode. A control electrode 24a is provided.

In Figure 7 I show a circuit embodying a tube made in accordance with my invention. The anode l5 of the triode section and the anode IQ of the tuning indicator section are electrically connected to each other through a resistor 25. The fluorescent anode is connected directly to a When no current flows from cathode/l3 there is no voltage drop in resistor 25 and the anode l5 and control electrode H, which is connected to it, are at substantially the same potential as the anode IQ of the tuning indicator section of the tube. Under these conditions the pattern of light forms a complete annulus as shown in Figure 3, and the anode fiuoresces' around its entire inner sloping surface. When a current flows in the circuit of the anode 15 a potential drop develops across the resistor 25 so that the anode I5 and control electrode I1 are made more negative with respect to the anode of the tuning indicator section of the tube 20, and approaches the potential of the cathode, producing a pattern of light such as indicated in Figure 2. The magnitude of the current through the triode portion of the tube is determined by the bias on the control grid [4.

In the circuit-shown, a diode detector or rectifler 21 has its anode 28 and its cathode 29 connected to opposite sides of the secondary of the intermediate or radio frequency transformer 32 tuned by condenser 36, the cathode being connected through the resistor 30 and by-pass condenser 3l. The cathode side of the transformer 32 is connected to the control grid l4 through resistor 33, the grid being by-passed by means of by-pass condenser 34 .so that a bias is impressed on the grid M. The conductor 35 may be connected to the automatic volume control circuit. In the arrangement shown with the set untuned and no signal passing through the transformer 32, no current passes through resistor 30 and no bias is developed. The grid I4 is at ground potential and permits current to flow through the triode section of the tube under which conditions the control electrode is at a potential near that of the cathode as described above, the light pattern takes the form shown in Figure 2. With the set tuned to a signal a rectified current passes through resistor 30 developing a drop across this resistor and impressing a bias on the control grid M of the triode through the resistor 33. This reduces the current passing through the triode in proportion to the bias impressed upon the grid so that the control electrode II becomes more'positive with respect to the cathode l3. The constants of the various elements are so chosen that when tuned to resonance the pattern of light is of the greatest width or forms a completely annular form such as shown in Figure 3.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed,

it will be apparent that my invention is by no area-ace means limited to the exact forms illustrated or the use indicated, but

be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims. 4

What I claim as new is:

1. An electron discharge device having an en- .veiope, a cathode within said envelope for emitting electrons, an anode surrounding said cathode and having its interior-surface coated with a fluorescent material for receiving electrons -from said cathode to produce a luminous annular shaped pattern on said anode, a control electrode 5 positioned between said anode and said cathode for determining the area of fluorescent surface of the anode reached by the electrons from said cathode and a grid surrounding said cathode between said cathode and control electrode and 20 adapted to be maintained at a potential not greater, than that of the cathode.

2. An electron discharge velope, a cathode within said envelope for emitting electrons, a dish-shaped anode surrounding 25 said cathode and having its interior surface coated with a. fluorescent material for receiving .electrons from said cathode to produce a pattern of light, a straight rod-like control electrode between .saigi cathode and said anode and parallel 0 to the cathode, and a grid surrounding said cathode between said cathode and control electrode and electrically connected to said cathode.

3. An electron discharge device having an envelope, a cathode within said envelope for emitting electrons, a dish-shaped anode surrounding said cathode-and provided with a fluorescent coating for receiving electrons from said cathode, a cup-shaped member positioned over the end of said cathode and electrically connected to said dish-shaped anode for confining the electrons from the cathode to the surface of the anode, and a control electrode comprising a straight rod-like member parallel to the cathode for determining that portion oi the surface of the 45 anode reached by electrons from the cathode to cause the anode to fluoresce, and a grid surrounding said cathode between said cathode and control electrode and electrically connected to said cathode.

4. An electron discharge device having an envelope, a straight thermionic cathode within said envelope having two separate emitting sections thereon, a grid and anode surrounding oneof said that many variations may device having an enemitting sections and a control electrode adjacent the other emitting section electrically connected to and supported by said anode, and a second anode concentric with and positioned around the other emitting section of the cathode and said control electrode and having a fluorescent coating on the interior thereof, and a cap over the end of said cathode and electrically connected to the coated anode, and a grid surrounding said cathode between said cathode and control electrode and electrically connected to said cathode. I

5. An electron discharge. device having an envelope, a cathode within said envelope for emitting electrons an anode surrounding said cathode and having its interior surface coated with a fluorescent material for receiving electrons from said cathode to produce a luminous annular shaped pattern on said anode, a control electrode positioned between said anode and said cathode and parallel to said cathode, and a grid having oppositely disposed side rods surrounding and closely'spaced from said cathode, said side rods being connected to said cathode, and a cupshaped member positioned over the end of the cathode and'having support members electrically connecting said cup-shaped member to said anode ffor confining the electrons from the cathode to he surface of the anode, said support members being parallel to and closely adjacent to the grid side rods for eliminating the shadow effects of said side rods during operation of the electron discharge device.

6. An electron discharge device having an envelope, a cathode within said envelope for emitting electrons, an anode surrounding said cathode and having its interior surface coated with a fluorescent material for receiving electrons from said cathode -to produce a luminous annular shaped pattern on said anode, a control electrode positioned between said anode and said cathode and parallel to said cathode, and a grid having oppositely disposed side rods surrounding and closely spaced from said cathode, said side rods being connected to said cathode, and a cupshaped member positioned over the end of the cathode, and ribbon-like support members electrically connecting said cup-shaped member to said anode and positioned parallel to and closely adjacent the side rods of said grid for eliminating the shadow efiects of said side rods during operation of the tube.

\ I HERBERT M. WAGNER.

positioned 

